This invention relates to a method of treatment useful in removing the harmful material from electrical products prior to their disposal. This invention is useful for example in treating a capacitor which is a roll of aluminum foil conductor and insulating paper impregnated with poly-chlorinated-biphenyl.
Poly-chlorinated-biphenyl (hereinafter referred to as PCB), a material frequently used in electrical products such as capacitors because of its dielectric strength, is hazardous to the environment. In order to safely dispose of electrical products which contain PCB, various well-known techniques are utilized to remove the PCB from the products. Thermal decomposition, radioactive decomposition, fermentative decomposition, reaction with sodium hydroxide at a high temperature, ultraviolet light decomposition, or decomposition by heat and a peroxide or sulfur are well-known techniques for treating liquid PCB. Notwithstanding the techniques which employ thermal decomposition, these techniques are not suitable for treating a roll of metal foil and paper which has been impregnated with PCB.
In removing harmful material from an electrical apparatus impregnated with PCB by thermal decomposition, the oil is first released from the body of the product and the body is broken into pieces. The pieces are then washed or dry distilled. If the washing or dry distillation removes all the PCB from the product, thermal treatment is not required prior to the product's disposal.
It is, however, practically impossible for conventional washing or dry distillation to completely remove all the harmful material from a roll of metal foil and paper such as a capacitor which has been impregnated with PCB. Hence, a final step of thermal treatment is usually required.
It is well known in the art that the complete thermal decomposition of PCB requires heating at a temperature of about 1200.degree. C., preferably 1400.degree. C. or more. The known methods for the thermal decomposition of PCB in electrical products such as capacitors possess many drawbacks. Heating electrical products at temperatures of 1200.degree. C. or more requires a heating device of large capacity, massive thermal insulation and if gas is used, equipment for a gas supply. Heating at a high temperature necessarily requires a large quantity of electrical energy or fuel which results in a high operating cost. Heating devices also require a long time to reach the desired temperature. Since the relationship between temperature and time is not linear in heating devices, a rise of 100.degree. C. between 1000.degree. C. and 1100.degree. C. requires a much greater time than the same temperature rise between 500.degree. C. and 600.degree. C., although it depends on the capacity of the heat source and the adequacy of the thermal insulation. Therefore, at high temperatures the efficiency of the heating devices declines greatly.
The object of this invention is to eliminate the drawbacks stated above while removing the harmful material from an electrical product. In particular this invention is useful in treating a roll of aluminum foil conductor and insulating paper such as a capacitor which has been impregnated with PCB.